JP2007525333A - Magnetically levitated high-speed spindle for forming irregular surfaces - Google Patents

Abstract

  A magnetically levitated high speed spindle assembly (20) is provided to form a non-circular hole (22) in the workpiece (24) or in a pin-shaped non-circular surface. The non-circular hole (22) can be formed at high speed and with high accuracy by means of an axial trajectory that varies in dimension. A rotary spindle (26) between a first magnetic bearing cluster (58) and a second magnetic bearing cluster (60) is supported and the bearing clusters (58, 60) are controlled separately to form This is accomplished by moving the tool (32) to the end of the spindle (26) in a predetermined elliptical path (B). A strategy that controls multiple inputs and multiple outputs is used to control the movement of the spindle (26) in the X and Y axes. Even if this multiple input and multiple output of the magnetic bearing cluster (58, 60) is controlled, the inclination angle between the cutting edge (34) of the forming tool (32) and the elliptical track (B) is perpendicular. This further improves the forming accuracy and stability of the spindle (26) while operating at high speeds.

Description

  This patent application claims priority to US Provisional Patent Application No. 60/547891, filed Feb. 26, 2004.

BACKGROUND OF THE INVENTION TECHNICAL FIELD The present invention relates generally to magnetically levitated high speed spindle assemblies for shaping non-circular surfaces, and more particularly to such assemblies for forming non-circular holes in a workpiece.

2. Related Technology Some product applications require the formation of non-circular holes. For example, in the manufacture of pistons for internal combustion engines, wrist pins or so-called pinholes formed for piston pins usually have a slight trumpet shape that opens towards the center to accommodate bending in the wrist pin Have In addition, this trumpet shape of the pinhole is optimally designed with a slight ellipticity, which causes the wrist pin to distort further as the wrist pin moves through various cycles. This trumpet shaped non-circular cross section of the pinhole must be formed with tight tolerances. For example, tolerances in the range of 3 to 5 microns are usually necessary to use these types.

  There are industrial methods for creating such non-circular holes with strict tolerance standards, including hydraulically operated milling tools and electrochemical machining techniques. The prior art also proposes drilling non-circular shapes using special machine tool spindles with active magnetic bearings. Active magnetic bearings operate according to the principle that the axis of rotation supported by the magnetic field generated by the electromagnet stator is formed from or by a ferromagnetic material. A control system with an appropriate power amplifier adjusts the magnetic field and holds the spindle in the desired radial position while the spindle rotates. Even if the load condition changes, this radial position can be maintained.

  The advantage of an active magnetic bearing system is that it controls the movement of the spindle and intentionally produces a deviation in the rotation of the spindle, which makes it possible to move the forming tool on the desired path. Nevertheless, the prior art has a number of drawbacks and limitations. For example, the shape of non-circular holes that can be created in particular in three dimensions is particularly limited. Furthermore, it is uncertain whether it is possible to accurately control the position of the cutting edge of the tool, and this allows the tolerance variation to be less than 5 microns. The object of the present invention is therefore to solve these problems and limitations.

SUMMARY OF THE INVENTION The present invention comprises a magnetically levitated high speed spindle assembly for forming a non-circular hole in a workpiece with dimensionally different axial trajectories. The assembly includes a spindle having a forming tool that defines a longitudinally extending axis and is secured at a forming end thereof. The first magnetic bearing cluster supports the spindle proximate to the forming tool for rotation in a magnetic levitation manner about the axis. The second magnetic bearing cluster is spaced from the first magnetic bearing cluster and supports the spindle at a location remote from the forming tool for magnetically levitating rotation about the axis. The radial bearing control device controls the first and second magnetic bearing clusters separately and adjusts the radial position of the shaft center while the spindle rotates in a magnetically levitated manner. The axis is moved at the end of the track. According to this aspect of the invention, the improvement comprises an axial motion control device for moving the forming tool along the axis about the workpiece while simultaneously changing the shape of the track. Therefore, a non-circular hole having a trajectory that continuously varies in the axial direction can be formed in the workpiece at high speed and with high accuracy. Thus, by controlling the magnetic bearing cluster and the axial position of the forming tool relative to the workpiece separately, but simultaneously, to form a non-circular hole having a continuously varying cross-sectional area and cross-sectional shape. Can do.

  According to a second aspect of the present invention, a magnetically levitated high speed spindle assembly is provided to form a non-circular hole in the workpiece. The assembly includes an elongate spindle that extends along an axis between a rear end and a molded end. The forming tool extends radially outward from the spindle close to the forming end and terminates with a disposed cutting edge. The first magnetic bearing cluster supports the spindle proximate to the molded end for rotation in a magnetic levitation manner about the axis. The second magnetic bearing cluster is spaced from the first magnetic bearing cluster and supports the spindle at a position remote from the forming end for rotation in magnetic levitation about the axis. The radial bearing control device separately controls the first and second magnetic bearing clusters, adjusts the radial position of the shaft center while the spindle rotates in a magnetically levitated manner, and forms a molded end on a predetermined non-circular track. It is provided to move the axis at the part. For this reason, the high-speed cutting edge forms a non-circular hole formed in a corresponding manner in the workpiece. According to this aspect of the invention, a cutting edge control device is provided to maintain a continuous tilt angle between the cutting edge and the track. The tilt angle has an optimum cutting angle determined by the radius extending from the axis to the cutting edge and the angle between the tangents to any point along the trajectory, where non-circular holes can be formed with improved accuracy The assembly can operate at higher rotational speeds while providing higher spindle stability.

  According to yet another aspect of the subject invention, a method for magnetically levitating a high speed spindle assembly is provided. This method is carried out in order to form irregular holes in the workpiece with dimensionally varying axial trajectories. The method includes fixing a radially extending forming tool to one end of a spindle having an axis, and a magnetic levitation region around a first region of the spindle proximate to the forming tool for rotation about the axis. Setting a magnetic levitation region around a second region of the spindle that is spaced from the first region and is remote from the forming tool, and first and second magnetic levitation By rotating the spindle about the axis in the region and separately varying the second flying region, the radial position of the axis is adjusted in the first and second regions while the spindle rotates. Adjusting and thereby moving the axis at the shaping end of the predetermined non-circular track. In this method, the first and second regions are formed simultaneously with the formation of irregular axially varying orbital holes in the workpiece by moving the forming tool along an axis relative to the workpiece. And a step of adjusting the radial position of the shaft center.

According to yet another aspect of the present invention, it is directed to a method for magnetically levitating a high speed spindle assembly. This method is carried out to form a non-circular hole in the workpiece, the step of forming a cutting edge in the forming tool, and the axial center so that the cutting edge is arranged radially outward from the axial center. Fixing a radially extending forming tool to one end of the spindle having, setting a magnetic levitation region around a first region of the spindle proximate to the forming tool for rotation about an axis; and Setting a magnetic levitation region around a second region of the spindle spaced from one region and remote from the forming tool, and without an axis in the first and second magnetic levitation regions Adjusting the radial position of the axial center in the first and second regions while rotating the spindle by rotating the spindle and varying the first and second flying regions; Ri and forming a non-circular hole in the workpiece by moving the cutting edge to a predetermined non-circular orbits. The improvement includes the step of maintaining a continuous tilt angle between the cutting edge and the track, so that non-circular holes can be formed with improved accuracy, and the spindle is more at higher rotational speeds. It becomes possible to operate with high stability. The tilt angle comprises an optimum cutting angle determined by the radius between the axis to the cutting edge and the angle between the tangent to any point along the non-circular track.

  The hole forming assembly, and the method according to the subject invention, expands the available range of hole shapes and configurations that can be formed at high speed and high precision, and in particular the problems and disadvantages of the prior art, particularly in the stereoscopic effect. Is a solution.

  These and other features and advantages of the present invention will be more readily understood when considered in conjunction with the following detailed description and the accompanying drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the figures, like reference numerals designate like or corresponding parts throughout the several views, and a magnetically levitated high speed spindle assembly is generally designated 20 in FIGS. Indicated by The spindle assembly 20 is of the type for forming a non-circular hole 22 in the workpiece 24. In FIG. 1, a workpiece 24 is shown for an embodiment that only comprises a piston for an internal combustion engine. Non-circular hole 22 is illustrated as a pinhole for including a wrist pin (not shown) as is well known in the prior art. However, the workpiece 24 may comprise any component and is not limited to piston, engine, or even automotive applications. Rather, it can be applied to non-circular holes 22 with high precision tolerances in any field of activity.

  The assembly 20 includes a rigid shaft spindle, indicated generally at 26, and extends along an axis A between a rear end 28 and a molded end 30. The forming tool 32 extends radially outward from the spindle 26 in the vicinity of the forming end 30 of the spindle and terminates at a pointed cutting edge 34. The forming tool 34 can comprise, for example, a removable cemented carbide tip having any commercially available shape. As shown in the cross-sectional view of FIG. 2, the forming tool 32 may be held by a detachable tool holder 36 that is fixed to the spindle 26 via a taper and bolt device 38. The spindle 26 includes a wrench surface 40 proximate the spindle back end 28 and the forming end 30 to facilitate removal of the forming tool 32 and replacement of the tool holder 36 for maintenance.

  The assembly 20 further includes a housing 42 through which the rear end 28 of the spindle and the molded end 30 of the spindle 26 extend. A drive motor, indicated generally at 44 in FIG. 2, is disposed within the housing 42 and operates to force the spindle 26 to rotate about the spindle axis A. The drive motor 44 may be of any known type and operates with alternating current or direct current. Alternatively, the drive motor 44 can be driven by fluid, driven by air, or driven by any other type of energy source. In the illustrated embodiment, the drive motor 44 includes an electric stator 46 that is secured within the housing 42 and a rotor or armature 48 that is secured to the spindle 26.

A pair of auxiliary bearings 50 are supported on opposite ends of the housing 42 and have a substantial clearance between the spindles 26. Since the auxiliary bearing 50 serves as a back-up safety mechanism, if the magnetic levitation system fails, the spindle 26 rotating at a high speed without damaging any components is supported by the auxiliary bearing 50. 50 can be safely stopped.

  In order to ensure proper axial alignment of the spindle 26 within the housing 42, a magnetic thrust bearing, indicated generally at 52, is inserted between the housing 42 and the spindle 26. The magnetic thrust bearing 52 includes two stators 54 disposed on the opposite side of the rotor disk 56. The stator 54 can be made of solid steel or a solid steel wedge with a radial groove in the middle of the wedge and can be filled with a laminate. The stator 54 is also filled with a coil and cancels the axial force in the region containing the rotor disk 56. Although not shown, assembly 20 may also include an axial position detector and power amplifier that operate in conjunction with thrust bearing 52 to determine and control the axial position of spindle 26.

  Reference is now made to FIG. A first magnetic bearing cluster, indicated generally at 58, supports the spindle 26 closest to the forming tool 32 for magnetic levitation rotation about the spindle axis A. Similarly, a second magnetic bearing cluster, indicated generally at 60, for rotating magnetically levitated about the axis A is magnetic bearing cluster for supporting the spindle 26 on the other side from the forming tool 32. 58 spaced from each other. In other words, the first magnetic bearing cluster 58 is close to the forming end 30 of the spindle 26, while the second magnetic bearing cluster 60 is close to the rear end 28 of the spindle 26.

  The first magnetic bearing cluster 58 includes at least three, and preferably four, magnetic stators that are equally spaced in a generally arcuate manner in a common plane perpendicular to the axis A. The magnet stators are typically arranged in pairs of a pair of opposing X coordinate magnet stators 62 and 62 'and a pair of opposing Y coordinate magnet stators 64 and 64'. X-coordinate stators 62 and 62 'include themselves in a so-called X-plane that penetrates the axis A diagonally and is oriented at an angle of about 45 degrees with respect to the horizontal plane. The upper X coordinate stator 62 is positioned above the axis A, while the lower X coordinate stator 62 'is positioned below the axis A. Y-coordinate stators 64 and 64 'are arranged in a so-called Y-plane that includes an axis A that is about 45 degrees with respect to the horizontal plane. The Y plane is perpendicular to the X plane. Thus, when the spindle 26 is perfectly centered within the first bearing cluster 58 and the second bearing cluster 60, the axis A coincides with the intersection of the X and Y planes. The bearing axis Z is formed by fixing the X plane to the Y plane and intersecting. Therefore, when the spindle 26 is in a neutral and centered position, the bearing axis Z and the axis A coincide. However, as spindle 26 is actuated by current fluctuations and other external shocks, axis A moves and rotates relative to a fixed bearing axis Z.

  Similarly, the second magnetic bearing cluster 60 includes X-coordinate stators 66 and 66 ′ and Y-coordinate stators 68 and 68 ′ that are oriented in the same manner as the stator of the first magnet bearing cluster 58. The X coordinate stators 62, 62 ', 66, 66' are all placed in the X plane, and the Y coordinate stators 64, 64 ', 68, 68' are all placed in the Y plane. In FIG. 3, these magnet stators are shown schematically as U-shaped fixed magnets. In practice, however, these stators can also be made of many laminated rings with electrodes on the inner diameter. Since the coil is wound around each electrode, each bearing cluster can be divided into four. Each of the four divided coils functions as a single electromagnet. As described and particularly in situations where the spindle 26 is supported in a generally horizontal state, the quadrant is aligned at 45 degrees from the vertical plane to distribute the gravitational reaction force.

Refer to FIG. 2 again. A first magnetic bearing cluster 58 is shown that includes a first rotor 70 disposed in a first region 72 of the spindle 26. The first rotor 70 is composed of a number of laminated rings that are attached to the sleeve and fitted to the spindle 26. Lamination is efficient to improve the response of the first magnetic bearing cluster 58. The second magnetic bearing cluster 60 also includes a second rotor 74 disposed in the second region 76 of the spindle 26. The first rotor 72 and the second rotor 74 are generally identical in structure, but may vary slightly in size and shape depending on the design application to the assembly 20.

  At least three, and preferably four, first position detectors are arranged in a common plane perpendicular to the axis A in a generally arcuately spaced manner and close to the first magnetic bearing cluster 58. Be placed. Preferably, as shown in FIG. 3, the first position detector includes a pair of opposing X coordinate detectors 78 and 78 ′ proximate to the first X coordinate stators 62 and 62 ′, respectively. A pair of opposing Y coordinate detectors 80 and 80 'are included adjacent to the corresponding Y coordinate stators 64 and 64'. Similarly, the opposing X-coordinate position detectors 82 and 82 'and Y-coordinate position detectors 84 and 84', which are the second position detectors, are respectively connected to the X-coordinate and Y-coordinate stators 66, 66 ', and 68. , 68 ′. All position detectors are activated by sending information about the position of the spindle 26 in the form of a voltage. Typically, these position detectors are adjusted so that the detector generates a zero voltage when the spindle 26 is neutral. A positive voltage is generated when the spindle 26 moves above the neutral position. If the spindle 26 moves below the neutral position, a negative voltage results.

  The radial bearing control device separately controls the first magnetic bearing cluster 58 and the second magnetic bearing cluster 60, and the radial direction of the axis A with respect to the bearing axis Z while the spindle 26 rotates magnetically levitated. Adjust the position. By separately controlling the position of the spindle 26 relative to the first magnetic bearing cluster 58 and the second magnetic bearing cluster 60, the axis A at the forming end 30 is adjusted and a highly controlled non-circular orbit B Will be able to draw. To adjust the molded end 30 as desired, the radial bearing controller may be of a centralized type that adjusts the input from all detectors and outputs to all bearing clusters.

  Alternatively, the radial bearing control device can include an X-axis control device 86 and a separate Y-axis control device 88. In this configuration, the X-axis control device 86 receives voltage signals from the X coordinate position detectors 78, 78 ′, 82, 82 ′, and measures, for example, the axial distance from the cutting edge 34 and the axis A to the cutting edge 34. This information is processed with a mathematical model that includes dimensional relationships such as tool radius and the current (or voltage) requirements are sent to an integrated or stand-alone amplifier. Therefore, the X-axis controller 86 receives a plurality of inputs, that is, inputs from all detectors in the X plane, and outputs a plurality of outputs to all the stators in the X plane view to dynamically control the spindle 26. . The X-axis controller 86 can include an anti-aliasing filter, an analog-to-digital converter, a digital signal processor, and a pulse width modulator. The voltage from position detectors 78, 78 ', 82, 82' passes through an anti-aliasing filter to remove high frequency noise from the signal. After the high frequency content is removed, the position signal is sampled by an analog-to-digital converter that converts the voltage signal into a form that can be processed by a digital signal processor. The digital information then passes through a digital filter and produces an output proportional to the amount of current (or voltage) required to correct or adjust the position of the spindle 26 according to a predetermined value. The requested current is compared to the actual current supplied to the magnetic bearing cluster 58, but that current is also sent, selected and sampled by an analog-to-digital converter. The error between the actual current and the requested current is used to characterize the pulse width modulated signal transmitted to the amplifier. This information is then transmitted to a pulse width modulator that generates a pulse width modulated waveform that is transmitted to the amplifier. Similarly, the Y-axis controller 88 receives a plurality of input signals from the Y coordinate detectors 80, 80 ′, 84, 84 ′ and performs a plurality of corrective actions via the output to the second magnetic bearing cluster 60. To work.

  The X-axis control device 86 and the Y-axis control device 88 can be designed for either class A tuning (Class A tuning) or class B tuning (Class B tuning). In the class B tuning, the current supply sent to the X coordinate stators 62, 62 ′, 66, 66 ′ by the X axis control device 86 increases and varies in a non-linear proportion between the opposing stators. To do. This method of class B tuning is useful for increasing the degree of freedom in generating the shape of the track B and also controls the rigidity and stability of the spindle 26 as it moves significantly away from the center of the bearing. To help.

  A thrust bearing controller 89 can be selectively configured to control the spindle 26 more strongly. As described above, the thrust bearing controller 89 receives an input from an axial position detector (not shown) and outputs a corrected output to the magnetic thrust bearing 52. In this case, as shown in FIG. 3, the thrust bearing control device 89 is controlled by the X-axis control device 58 and the Y-axis control so as to intentionally operate the magnetic thrust bearing 52 together with the radial bearings 62, 64, 66, 68. It can be transmitted to the device 60. Alternatively, in a centralized bearing controller embodiment that controls all bearings from a single end, the radial and thrust bearings can be adjusted and controlled in this way.

  Reference is now made to FIG. The movement of the forming tool 32 when the axis A moves around the track B is shown. The forming tool 32 shown is solid and comprises a spindle axis A which is offset from the bearing axis Z. The point of evaluation is determined by the point where the cutting edge 34 contacts the non-circular hole 22 of the workpiece 24. The line drawn from the bearing axis Z to the cutting edge 34 has a shape radius 90. The line drawn from the bearing axis Z to the axis A has a track radius 92. The line drawn from the axis A to the cutting edge 34 has a tool radius 94. In a preferred embodiment of the present invention, the angle of inclination, ie the angle of the tool radius 94 with respect to the tangent 96 on the track B, remains constant and is preferably at right angles throughout the forming operation. The tool radius 94 also remains perpendicular to the tangent line 98 drawn at the point of contact with the hole 22. As shown virtually in FIG. 4, this tilt angle remains consistent throughout the movement of the axis A around the trajectory B. Adjusting and controlling the first magnetic bearing cluster 58 and the magnetic bearing cluster 60 using a strategy that controls multiple inputs and multiple outputs is thus maintained. It is necessary to achieve a continuous tilt angle. Even if the angle 100 between the shape radius 90 and the trajectory radius 92 varies between positive and negative values throughout the trajectory cycle, this continuous, preferably right-angle tilt angle is maintained. By using the X-axis controller 86 and the Y-axis controller 88 to control the first magnetic bearing cluster 58 and the second magnetic bearing cluster 60, respectively, a continuous inclination angle between the cutting edge 34 and the track B can be obtained. Therefore, the non-circular hole 22 can be formed with high accuracy. Also, keeping the tilt angle at all points along the trajectory B allows the assembly 20 to operate at higher rotational speeds and higher spindle stability because the reaction force from the forming tool 32 is This is because it hardly fluctuates. Of course, the optimum tilt angle may be other than 90 ° and the controllers 86 and 86 'can be programmed to maintain the optimum angle throughout the molding cycle.

A rotational position detector in the form of a rotary encoder 102 for determining the angular position of the spindle 26 and consequently the position of the forming tool 32 with respect to the axis A is schematically illustrated in FIG. The rotary encoder 102 can communicate with the X-axis control device 86 and the Y-axis control device 88 to adjust the first magnetic bearing cluster 58 and the second magnetic bearing cluster 60. These control devices 86 and 88 are designed so that the forming tool 32 completes one revolution around the axis A and at the same time the forming end 30 of the spindle 26 completes one turn around the track B. 32 is preferably controlled. This makes it easy to maintain the optimum tilt angle by sweeping the trajectory B completely. However, due to the complex shape of the hole 22, it may be necessary to lift the forming tool 32 from the surface of the hole 22 as the spindle 26 moves. Therefore, it may be necessary to rotate the forming tool 32 a plurality of times for each round around the track B depending on the shape of the complicated hole.

  The axial motion control device is shown schematically at 104 in FIG. The axial motion controller 104 moves the forming tool 32 to the workpiece 24 in a direction generally parallel to the axis A, while the forming tool 32 forms the non-circular hole 22. At the same time, the controllers 86 and 88 actuate the magnetic bearing clusters 58 and 60, resulting in a dimensional variation in the axial trajectory of the hole 22 in the workpiece 24. The axial motion control device 104 is operable by holding the fixed workpiece 24 and moving the spindle assembly 20 or moves relative to the fixed spindle assembly 20 as shown in FIG. A workpiece holder 106 may be included. Alternatively, both components can move simultaneously.

  By combining axial movements associated with an axis or a continuously varying trajectory B, it is possible to create geometrically complex shapes as shown in FIG. In this case, the hole 22 is shown having a generally elliptical cross section at the opening of the workpiece 24, where the ellipse has a generally vertical major axis 108. As the hole 22 extends deeper into the workpiece 24, the major axis 108 rotates in a clockwise direction while the size of the ellipse decreases. This is illustrated by a virtual elliptical cross-sectional view at midpoint 110. As the hole 22 continues to extend deeper into the workpiece 24, the shape of the hole 22 expands, while the major axis 108 continues to rotate clockwise until the end point 112 is reached, where the elliptical major axis 108 then becomes generally horizontal. The complex and dimensionally varying axial trajectory of the hole 22 in the workpiece 24 is not limited to the configuration shown in FIG. For example, FIG. 6 shows a non-elliptical irregular hole 22 'in the form of a 2-lobed cam. Alternatively, FIG. 7 shows a multi-lobed shape of the hole 22 ″. As will be apparent to those skilled in the art, the subject spindle assembly 20 and the multiple inputs and outputs of the controllers 86 and 88 are used to create almost any geometrically conceivable shape. be able to.

  Figures 8 and 9 show various alternatives to the forming tool 32 'that can use more than one cutting edge 34'. Alternatively, the cutting edge 34 "can extend continuously around the shaped end 30" in the form of a grinding disk or grinding wheel (not shown).

  10 and 11 illustrate the possibility of orientation of the end spindle 26 by the theoretical circles 114 and 116, and the first of the spindle 26 in the first magnetic bearing cluster 58 and the second magnetic bearing cluster 60, respectively. The maximum range of motion of region 72 and second region 76 is shown. The cutting radius of the cutting edge 34 is indicated by a virtual theoretical circle 118. As will be apparent, an infinite variety that can vary continuously in the axial direction by a strategy that controls multiple inputs and multiple outputs arranged by the controllers 86 and 88 operating within the possible range of motion described. The shape of the hole 22 can be used. And this control strategy can be easily adapted to high-speed manufacturing operations. For example, in a high-speed manufacturing operation, the spindle 26 is driven at a speed higher than 10,000 rpm.

  Despite the fact that exemplary embodiments of the invention have been described in the more conventional sense in connection with pore formation, it will be apparent to those skilled in the art that these novel techniques can be performed on the outer surface. it can. Therefore, it is possible to form a non-circular surface only by directly deforming the forming tool 34 to the number of male parts. Therefore, the present invention contemplates a surface molding method and apparatus that can be used with the same effect on holes with dimensionally varying tracks and holes and pin-like features that require non-round shapes. Is.

  Obviously, many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it will be appreciated that the invention may be practiced otherwise than as specifically described herein without departing from the scope of the appended claims.

  The invention is defined by the claims.

FIG. 2 is a schematic front view of a spindle assembly according to the subject invention and a piston workpiece prepared for manipulation to form a hole. 1 is a schematic cross-sectional view of a magnetically levitated high speed spindle assembly according to the present invention. A magnetically levitating between a first and a second magnetic bearing cluster comprising a respective radial bearing controller for the magnet stator and a position detector in the respective X and Y coordinate planes 1 is a schematic diagram showing a spindle according to the invention. FIG. 6 is an enlarged cross-sectional view of a non-circular hole formed in a workpiece using a forming tool, virtually showing various positions around the track. FIG. 2 is a schematic perspective view showing a typical hole geometry of a workpiece, where a continuously axially varying track is created by a forming tool. Fig. 5 shows another exemplary non-circular hole geometry with two irregular lobes. FIG. 7 is a view similar to FIG. 6 further illustrating the geometry of yet another non-circular hole having a plurality of lobes. FIG. 5 is an end view of an alternative forming tool configuration including two opposing cutting edges. FIG. 9 is an end view similar to FIG. 8 further illustrating yet another alternative embodiment of a forming tool including a plurality of cutting edges. FIG. 3 is a schematic view of a spindle assembly showing the range of upper and lower trajectories in the first and second magnetic bearing clusters in a situation where the spindle axis remains parallel throughout its trajectory. FIG. 11 is a view similar to FIG. 10 showing the extent of the end of the track when the spindle is controlled by the first and second magnetic bearing clusters at opposite end limits.

Claims (74)

A magnetically levitated high speed spindle assembly for forming a non-circular hole in a workpiece with a dimensionally varying axial trajectory, the assembly comprising:
A spindle defining a longitudinally extending axis and having a forming tool secured at its forming end;
A first magnetic bearing cluster for supporting the spindle proximate to the forming tool to rotate in a magnetically levitated manner about the axis;
A second magnetic bearing cluster disposed at a distance from the first magnetic bearing cluster and supporting the spindle at a position away from the forming tool for rotating in a magnetically levitated manner about the axis; ,
The first magnetic bearing cluster and the second magnetic bearing cluster are separately controlled to adjust the radial position of the shaft center while the spindle rotates in a magnetically levitated manner. A radial bearing control device for moving the axis at the molded end in a non-circular track;
While moving the forming tool along the axis with respect to the workpiece, the shape of the track is changed at the same time, thereby creating a non-circular hole with a continuously varying axial track in the workpiece at high speed. And an axial motion control device that can be formed with high precision,
An assembly comprising:   The assembly of claim 1, wherein the first magnetic bearing cluster includes at least three magnet stators that are equally spaced in a generally arcuate manner in a common plane about the axis.   And at least three first position detectors disposed in the common plane, centered on the axis, and spaced generally equidistantly in proximity to the at least three magnet stators of the first magnetic bearing cluster. The assembly of claim 2, comprising:   4. The assembly of claim 3, wherein the second magnetic bearing cluster includes at least three magnet stators that are equally spaced in a generally arcuate manner in a common plane about the axis.   And at least three second position detectors disposed in the common plane and generally spaced apart in a generally arcuate manner about the axis and in proximity to the at least three magnet stators of the second magnetic bearing cluster. The assembly of claim 4 comprising:   The first magnetic bearing cluster includes a pair of opposing X coordinate magnet stators and a pair of opposing Y coordinate magnet stators, the X coordinate magnet stator being between the Y coordinate magnet stators. 2. The assembly of claim 1, wherein the assemblies are generally coplanar and spaced apart.   The radial bearing control device includes a pair of opposed X coordinate position detectors proximate to the pair of opposed X coordinate magnet stators of the first magnetic bearing cluster, and the first magnetic bearing cluster of the first magnetic bearing cluster. The assembly of claim 6 including a pair of opposing Y coordinate position detectors proximate to the pair of opposing Y coordinate magnet stators.   The first magnetic bearing cluster is disposed in a first region of the spindle in the common plane formed between the corresponding X coordinate magnet stator and the Y coordinate magnet stator. The assembly of claim 7 including a rotor. The second magnetic bearing cluster includes a pair of opposing X-coordinate magnet stators and a pair of opposing Y-coordinate magnet stators, the X-coordinate magnet stators comprising the opposing Y-coordinate magnet stators. 9. The assembly of claim 8, wherein the assembly is spaced apart and generally coplanar.   The radial bearing control device includes a pair of opposed X coordinate position detectors proximate to the pair of opposed X coordinate magnet stators of the second magnetic bearing cluster, and the second magnetic bearing cluster of the second magnetic bearing cluster. 10. The assembly of claim 9, comprising a pair of opposing Y coordinate position detectors proximate to the pair of opposing Y coordinate magnet stators.   The second magnetic bearing cluster is disposed in a second region of the spindle in the common plane formed between the corresponding X coordinate magnet stator and the Y coordinate magnet stator. The assembly of claim 10 including a rotor.   The radial bearing controller includes a variable current generator for varying the supply of current to each of the pair of X coordinate magnets of the first bearing cluster in a non-linearly proportional manner. The assembly according to claim 9.   The assembly of claim 1, wherein the axial motion control device includes a workpiece holder.   The assembly of claim 1, further comprising a rotational position detector for determining an angular position of the forming tool about the axis.   15. An assembly according to claim 14, wherein the forming end has finished one revolution around the track at the same time as the forming tool has completed one revolution about the axis.   The assembly of claim 1, wherein the forming tool terminates in a plurality of point-like cutting edges that are equally spaced in a generally arcuate manner about the axis.   The assembly of claim 1, wherein the forming tool terminates with a single pointed cutting edge.   A cutting edge control device for maintaining a continuous inclination angle between the cutting edge and the track, wherein the inclination angle is a radius extending from the axis to the cutting edge, and an arbitrary point along the track 18. The assembly of claim 17, further comprising a cutting edge control device with an optimum cutting angle defined by the angle between tangents to.   The assembly of claim 18, wherein the tilt angle is substantially perpendicular.   The assembly of claim 18, wherein the track is an irregular shape.   The assembly of claim 1, further comprising a housing.   24. The assembly of claim 21, further comprising a magnetic thrust bearing associated with the spindle to limit axial movement of the spindle relative to the housing.   24. The assembly of claim 21, further comprising a drive motor disposed within the housing for forcibly rotating the spindle about the axis.   The assembly of claim 21, wherein the housing includes at least two auxiliary bearings. A magnetically levitated high speed spindle assembly for forming a non-circular surface on a workpiece, the assembly comprising:
An elongated spindle extending along the axis between the rear end and the molded end;
A molding tool extending radially outward from the spindle proximate to the molding end and terminating in a point-like cutting edge;
A first magnetic bearing cluster that supports the spindle proximate to the molded end for rotating in a magnetically levitated manner about the axis;
A second magnetic bearing cluster that is spaced apart from the first magnetic bearing cluster and supports the spindle at a position away from the forming end for rotation in a magnetically levitated manner about the axis. When,
The first magnetic bearing cluster and the second magnetic bearing cluster are separately controlled to adjust the radial position of the shaft center while the spindle rotates in a magnetically levitated manner, so that a predetermined non-circular orbit is obtained. The molding end, so that the cutting edge forms a corresponding non-circular hole in the workpiece, and a radial bearing control device,
A cutting edge control device for maintaining a continuous inclination angle between the cutting edge and the track, wherein the inclination angle is a radius extending from the axis to the cutting edge, and an arbitrary point along the track With an optimum cutting angle defined by the angle between the tangent to the non-circular hole can be formed with improved accuracy, allowing the assembly to operate at higher rotational speeds and higher spindle stability A cutting edge control device,
An assembly comprising:   26. The assembly of claim 25, wherein the tilt angle is substantially perpendicular.   26. The assembly of claim 25, wherein the track is an irregular shape.   26. The assembly of claim 25, wherein the first magnetic bearing cluster includes at least three magnet stators that are equally spaced in a generally arcuate manner in a common plane about the axis.   And at least three first position detectors disposed in the common plane, centered on the axis, and spaced generally equidistantly in proximity to the at least three magnet stators of the first magnetic bearing cluster. 30. The assembly of claim 28, comprising.   30. The assembly of claim 29, wherein the second magnetic bearing cluster includes at least three magnet stators that are equally spaced in a generally arcuate manner in a common plane about the axis.   And at least three second position detectors disposed in the common plane and generally spaced apart in a generally arcuate manner about the axis and in proximity to the at least three magnet stators of the second magnetic bearing cluster. 32. The assembly of claim 30, comprising.   The first magnetic bearing cluster includes a pair of opposing X coordinate magnet stators and a pair of opposing Y coordinate magnet stators, the X coordinate magnet stator being between the Y coordinate magnet stators. 26. The assembly of claim 25, spaced apart and generally coplanar.   The radial bearing control device includes a pair of opposed X coordinate position detectors proximate to the pair of opposed X coordinate magnet stators of the first magnetic bearing cluster, and the first magnetic bearing cluster of the first magnetic bearing cluster. 35. The assembly of claim 32, comprising a pair of opposing Y coordinate position detectors proximate to the pair of opposing Y coordinate magnet stators. The first magnetic bearing cluster is disposed in a first region of the spindle in the common plane formed between the corresponding X coordinate magnet stator and the Y coordinate magnet stator. 34. The assembly of claim 33, comprising a rotor.   The second magnetic bearing cluster includes a pair of opposing X-coordinate magnet stators and a pair of opposing Y-coordinate magnet stators, the X-coordinate magnet stators comprising the opposing Y-coordinate magnet stators. 35. The assembly of claim 34, disposed between and generally coplanarly spaced.   The radial bearing control device includes a pair of opposed X coordinate position detectors proximate to the pair of opposed X coordinate magnet stators of the second magnetic bearing cluster, and the second magnetic bearing cluster of the second magnetic bearing cluster. 36. The assembly of claim 35, comprising a pair of opposing Y coordinate position detectors proximate to the pair of opposing Y coordinate magnet stators.   The second magnetic bearing cluster is disposed in a second region of the spindle in the common plane formed between the corresponding X coordinate magnet stator and the Y coordinate magnet stator. 38. The assembly of claim 36, comprising a rotor.   The radial bearing controller includes a variable current generator for varying the supply of current to each of the pair of X coordinate magnets of the first bearing cluster in a non-linearly proportional manner. 36. The assembly according to 35.   26. The assembly of claim 25, further comprising a rotational position detector for determining an angular position of the forming tool about the axis.   40. The assembly of claim 39, wherein the forming end has completed one revolution around the track at the same time as the forming tool has completed one revolution about the axis.   While moving the forming tool along the axis with respect to the workpiece, the shape of the track is changed at the same time, thereby creating a non-circular hole with a continuously varying axial track in the workpiece at high speed. 26. The assembly of claim 25, further comprising an axial motion control device that can be formed with high precision.   42. The assembly of claim 41, wherein the axial motion control device includes a workpiece holder.   26. The assembly of claim 25, further comprising a housing.   44. The assembly of claim 43, further comprising a magnetic thrust bearing associated with the spindle to limit axial movement of the spindle relative to the housing.   44. The assembly of claim 43, further comprising a drive motor disposed within the housing for forcibly rotating the spindle about the axis.   44. The assembly of claim 43, wherein the housing includes at least two auxiliary bearings. A method for magnetically levitating a high speed spindle assembly for forming irregular holes in a workpiece having dimensionally varying axial trajectories, the method comprising:
Fixing a radially extending molding tool to one end of a spindle having an axis;
Setting a magnetic levitation region around a first region of the spindle proximate to the forming tool for rotation about an axis;
Setting a magnetic levitation region around a second region of the spindle spaced from the first region and remote from the forming tool;
Rotating the spindle about the axis within the first and second magnetic levitation regions;
By varying the first and second magnetic levitation regions, the radial position of the axial center is adjusted in the first and second regions while the spindle rotates, thereby providing a predetermined non-circular orbit. Moving the molding end;
Simultaneously with the step of adjusting the radial position of the axial center in the first and second regions, different orbits in the irregular axial direction in the workpiece by moving the forming tool along the axial center with respect to the workpiece. Forming a hole in the
A method comprising:   The step of setting a magnetic levitation region around a first region of the spindle includes positioning at least three detectors that are spaced generally equidistantly in a common plane about a shaft center in a common plane. 48. A method according to item 47.   The step of setting a magnetic levitation region around a second region of the spindle comprises positioning at least three detectors that are spaced generally equidistantly in a common plane about a shaft center in a common plane. Item 49. The method according to Item 48.   Adjusting the radial position of the axial center in the first and second regions, the at least three first position detectors centered on the axial center proximate to the at least three magnet stators in the first region; And at least three first position detectors in proximity to the at least three magnet stators in the second region and centered on the common axis. 52. The method of claim 49, comprising generally equally spaced arcs.   The step of setting a magnetic levitation region around the first region of the spindle positions a pair of opposing X coordinate magnet stators and a pair of opposing Y coordinate magnet stators, and X coordinate magnet fixing 48. The method of claim 47, including disposing the child between opposing Y coordinate magnet stators and generally coplanarly spaced.   The step of setting a magnetic levitation region around the second region of the spindle positions a pair of opposing X coordinate magnet stators and a pair of opposing Y coordinate magnet stators, and X coordinate magnet fixing 52. The method of claim 51 including disposing the child between opposing Y coordinate magnet stators and generally coplanarly spaced.   53. The method of claim 52, further comprising varying the supply of current to each of the pair of X coordinate magnets of the first bearing cluster in a non-linear equal proportion.   53. The method of claim 52, wherein the step for adjusting the radial position of the axial center in the first and second regions includes securing a position detector proximate to each of the magnetic stators.   48. The method of claim 47, wherein the step of moving the forming tool relative to the workpiece includes moving the workpiece while keeping the spindle axially fixed.   48. The method of claim 47, further comprising instantaneously determining an angular position of the forming tool about the axis during the step of forming the hole.   57. The method according to claim 56, further comprising the step of timing the angular velocity of the forming tool such that the forming end has completed one revolution around the track while the forming tool has completed one revolution about the axis. A step to maintain a continuous tilt angle between the cutting edge and the track of the forming tool, the tilt angle being determined by the radius extending from the axis to the cutting edge and the angle between the tangent to any point along the track 48. The method of claim 47, further comprising providing an optimal cutting angle to be achieved.   59. The method of claim 58, wherein the step of maintaining a continuous tilt angle comprises maintaining the tilt angle substantially at a right angle.   59. The assembly of claim 58, further comprising directing the track into an irregular shape. A method for magnetically levitating a high speed spindle assembly for forming a non-circular hole in a workpiece, the method comprising:
Forming a cutting edge on the forming tool;
Fixing a radially extending forming tool at one end of a spindle having an axis such that the cutting edge is radially outward from the axis;
Setting a magnetic levitation region around a first region of the spindle proximate to the forming tool for rotation about an axis;
Setting a magnetic levitation region around a second region of the spindle spaced from the first region and remote from the forming tool;
Rotating the spindle about the axis within the first and second magnetic levitation regions;
By varying the first and second flying regions, the radial position of the shaft center is adjusted in the first and second regions while the spindle is rotating, thereby cutting into a predetermined non-circular orbit. Moving the blade to form a non-circular hole in the workpiece and maintaining a continuous inclination angle between the cutting edge and the track, the inclination angle being a radius extending from the axis to the cutting edge and a non-circular shape With an optimum cutting angle determined by the angle between the tangents to any point along the trajectory, so that non-circular holes can be formed with improved accuracy and the spindle has a higher rotational speed And steps that become operable with higher stability;
A method comprising:   62. The method of claim 61, wherein the step of maintaining a continuous tilt angle comprises maintaining the tilt angle substantially at right angles.   62. The assembly of claim 61, further comprising directing the track into an irregular shape.   62. The method of claim 61, further comprising instantaneously determining an angular position of the forming tool about the axis during the step of forming the hole.   65. The method of claim 64, further comprising the step of timing the angular speed of the forming tool such that the forming end completes one revolution around the axis while the forming tool completes one revolution about the axis.   By moving the forming tool along the axis with respect to the workpiece, the irregular axial holes in the workpiece are formed in different radial paths, and at the same time in the radial direction of the axis in the first and second regions. 62. The method of claim 61, further comprising the step of adjusting the position.   68. The method of claim 66, wherein the step of moving the forming tool along the axis with respect to the workpiece comprises moving the workpiece while keeping the spindle axially fixed. The step of setting a magnetic levitation region around a first region of the spindle includes positioning at least three detectors that are spaced generally equidistantly in a common plane about a shaft center in a common plane. Item 62. The method according to Item 61.   The step of setting a magnetic levitation region around a second region of the spindle comprises positioning at least three detectors that are spaced generally equidistantly in a common plane about a shaft center in a common plane. Item 69. The method according to Item 68.   Adjusting the radial position of the axial center in the first and second regions, the at least three first position detectors centered on the axial center proximate to the at least three magnet stators in the first region; And at least three first position detectors in proximity to the at least three magnet stators in the second region and centered on the common axis. 70. The method of claim 69, comprising generally equally spaced arcs.   The step of setting a magnetic levitation region around the first region of the spindle positions a pair of opposing X coordinate magnet stators and a pair of opposing Y coordinate magnet stators, and X coordinate magnet fixing 62. The method of claim 61, comprising disposing the child between opposing Y coordinate magnet stators and generally coplanarly spaced.   The step of setting a magnetic levitation region around the second region of the spindle positions a pair of opposing X coordinate magnet stators and a pair of opposing Y coordinate magnet stators, and X coordinate magnet fixing 72. The method of claim 71, comprising disposing the child between opposing Y coordinate magnet stators and generally coplanarly spaced.   73. The method of claim 72, further comprising varying the supply of current to each of the pair of X coordinate magnets of the first bearing cluster in a non-linear equal proportion.   73. The method of claim 72, wherein the step for adjusting the radial position of the axis in the first and second regions includes securing a position detector proximate to each of the magnetic stators.

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